The invention generally relates to force sensing mechanisms and more particularly to one such sensor capable of measuring the tensile force produced within a buckled-up seat belt system and more particularly the lap belt.
The present invention is an improved force sensing mechanism characterized by low dead zone, hysteresis and sliding friction, ease of assembly and reduced cost.
It is a further object of the present invention to provide a force sensor or force sensing mechanism that is usable in cooperation with other sensors (including a weight sensor) to determine the normal force on a vehicle seat, which is produced in part by the weight of the object or person on the seat and the tension within a seat belt system.
The present invention defines an electronic force sensor for use in a seat belt system. The sensor includes a number of interconnected parts, some of which are relatively movable and mutually spring loaded. As a result of manufacturing tolerances the electrical output of the sensor, which follows its force-deflection characteristic, may include a dead zone or may display hysteresis. It is an object to provide a force sensor that includes a compensating feature to reduce or otherwise eliminate dead zone and/or hysteresis.
Accordingly the invention comprises: a force-sensing mechanism comprising: a housing, which can include first and second housing members; a slidable member or plate positioned within the housing such as between portions of the first and second housing members and moveable thereto; various spacers located between the housing and the sliding plate to space and stabilize the sliding plate relative to the first and second housing members; a magnetic sensor stationarily mounted between the first and second housing members, a magnet moveable with the sliding plate in response to forces applied across the housing and to the sliding plate; a spring assembly having one end in operative engagement with the sliding plate and another end in operative engagement with the housing to bias the sliding plate within the housing. The spring assembly includes an adjustment mechanism that is used to calibrate the force sensor and in calibrating the sensor, the dead zone is eliminated and hysteresis reduced or eliminated. This adjustment mechanism creates a greater uniformity from sensor to sensor.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.